PulseNet detected a multistate cluster of Salmonella Newport infections with an indistinguishable pulse-field gel electrophoresis (PFGE) pattern in August 2014.
A total of 275 patients in 29 states and the District of Columbia were identified, with illness from May 20–September 30, according to the morbidity and mortality weekly report (MMWR).
An additional 18 suspected cases were excluded from the analysis because they were unlikely to be related.
Cucumbers were novel source
Epidemiologic data, traceback investigations, whole genome sequencing (WGS) all support the hypothesis cucumbers were a likely source of Salmonella Newport infections.
It was the first multistate outbreak of the pathogen implicating a fresh produce item grown in the Delmarva region other than tomatoes.
Outbreaks of illnesses associated with the PFGE pattern identified have been linked to tomatoes harvested from Virginia's Eastern Shore in the Delmarva region but not to cucumbers or other produce items.
A definitive contamination source has not been found and the pathogen was not isolated directly from any Delmarva region tomatoes and animals have also been ruled out as the source.
Median age of patients was 42 years; 66% (174 of 265) were female. 34% (48 of 141) were hospitalized and one death was reported in an elderly man with bacteremia.
Informational traceback
Eight plants in Maryland and Delaware received cucumbers from a single distributor.
Preliminary traceback from the distributor to several brokers identified a common grower on Maryland's Eastern Shore in the Delmarva region.
Officials collected 48 environmental samples from areas where cucumbers were grown, harvested, and packed. Sediment and manure samples were taken from the farm. No samples yielded Salmonella but it was performed several months after the harvest.
Records and interviews indicated the farm applied poultry litter 120 days before harvest, but it was not available for testing.
Interviews of ill persons by state and local health officials found that travel to the Delmarva region during the incubation period was common.
A total of 101 patients were interviewed using the supplemental questionnaire about exposures in the week before illness onset.
Sixty-two percent (49 of 79) of respondents reported eating cucumbers in the week before becoming ill. Patients were significantly more likely to report consuming cucumbers compared with the 2006–2007 FoodNet Population Survey.
The proportion of ill persons who ate tomatoes, leafy greens, or any other item on the questionnaire was not significantly higher than expected compared with the FoodNet Population Survey.
The Maryland Department of Agriculture plans additional assessments in the Delmarva region before the 2015 planting season to see if additional or alternative "best practices" can be implemented.
Cucumbers should be washed thoroughly, scrubbed with a clean produce brush before peeling or cutting, and refrigerated as soon as possible to prevent bacteria growth.